This invention relates to a filter insert comprising an annular filter element connected in a fluid-tight manner on one axial end face to a cover and on an opposite axial end face to a base, and having a central channel communicating with a central opening in the cover and having a central tube situated therein extending between the cover and the base.
Filter inserts comprising a filter element fixedly connected to a cover and a base are known in general and are used as replaceable filter cartridges. To ensure adequate stability of the filter element, such filters usually have a central tube running between the cover and the base in the central channel of the filter element. The central channel thus communicates with an opening in the cover, which usually forms the outlet from the filter. To ensure adequate stability of the filter insert, the central tube should always extend from the base to the cover of the filter. The filter element usually comprises filter paper in lamellar folds or other filter media. Such a filter bellows may have considerable tolerances in its dimensions. To ensure that the central tube extends between the cover and the base, there must be a narrow tolerance in the filter element or central tubes of different lengths must be made available.